In this developmental application (R21), we propose to develop and test the impact of a trans-community approach to the prevention of weight-gain in a predominantly Mexican-American population. We will recruit at-risk and overweight (BMI >85th percentile) 3rd and 4th grade children, and their parents/primary caregivers, from 3 elementary schools to participate in the program and undergo assessments (baseline, 6, 9,12, and 18 months) of BMI, body composition, physical activity, diet and psychosocial factors related to behavior change and weight. The 3 schools, matched on student demographics, will be randomly assigned to 1 of the following 3 interventions: Level 1 - a school-based program that meets state mandated standards for nutrition and physical activity; Level 2 - the school-based program plus an after- school physical activity and nutrition program; and Level 3 - the school-based and after-school programs plus a family-based physical activity and nutrition program. The Level 1 program represents the minimal requirement of nutrition and physical activity programs for Arizona schools and is the equivalent of the "standard of care" in medical research. The Level 1 school will serve as the comparison group. Building on the "standard of care" by adding an after-school program (Level 2) and a family component (Level 3) will allow us to assess the contribution that each added component (i.e., after-school program and family intervention) makes to a typical school-based program. Furthermore, integrating the Level 1 and Level 2 programs into the Level 3 program will allow assessment of the contribution of the family component to these programs. The interventions will incorporate existing programs that have been developed by our research team and capitalize on existing relationships between our team, the schools and the community. Moreover, the trans-community approach is not only reflected in the design of the interventions but in the collaborations between the University of Arizona, Pima County (via the Expanded Food and Nutrition Education Program), the Sunnyside School District and the YMCA to reduce and prevent childhood obesity. Building on existing programs and collaborations with widespread organizations (Cooperative Extension and YMCA) is expected to promote sustainability and rapid dissemination. [unreadable] [unreadable]